In many cases, manufacturers are promoting their foods as pick-me-ups, but they're not labeling how much caffeine is included in the products. Currently, the Food and Drug Administration does not require it. And that's raising some questions about how much caffeine we're getting these days.

"I think at a minimum the FDA should require the amount of caffeine to be disclosed on product labels," says Jacobson. And some caffeine researchers seem to agree.

"Caffeine is a drug," explains Abraham Palmer of the University of Chicago. And partly because of genetic differences, "there's a lot of variation in the way people experience the effects of caffeine."

Palmer says he loved caffeine from the day he had his first cup of coffee at age 14. It gives him a lift and makes him feel more alert. But "there are others, such as my wife, who really hate caffeine, because it makes them feel jittery and anxious."

Given that some people are sensitive to even small shifts in caffeine consumption, Palmer says is would be helpful to consumers if manufacturers had to label amounts. "It's hard for me to see what the downside would be," says Palmer.

And Jennifer Temple of the University of Buffalo, who studies how adolescents respond to caffeine, says: "The more information you can give consumers and parents about the caffeine content in beverages and foods, the better. It allows them to make more informed decisions."

If you listen to my story, you'll hear about one of Temple's research studies that suggest teenage boys seem to be motivated to seek out caffeine after they're exposed to it for a short period. And other studies have shown that caffeine has a reinforcing effect on consumption. Meaning if someone drinks coffee and experiences a pleasant buzz, it reinforces a coffee habit.

This doesn't make caffeine dangerous, but it raises questions about how it's regulated.

"I think it's a real concern to add a mildly addictive stimulant drug to all kinds of things. And it's a special risk to kids," says Jacobson.

Jacobson raised a stink when Frito-Lay, maker of the iconic molasses-coated peanut and popcorn Cracker Jack candy with the prize inside, announced plans for its new line of snacks called Cracker Jack'd, some of which will contain coffee.

But Frito-Lay says it is not marketing these products to children. "All marketing for the products will be exclusively aimed at adult consumers," Alexia Allina of Frito-Lay told us in an email. "And the presence of coffee and the caffeine that comes with it is clearly called out on both the front and back of the package."

Owing to the varying caffeine content of coffee, Frito-Lay says the caffeine content in its snack may vary, too. But in general, it expects the snack to contain approximately 70 mg (equivalent to about two-thirds of a cup of coffee) of caffeine in each 2-ounce package.

Copyright 2013 NPR. To see more, visit http://www.npr.org/.

Transcript

ROBERT SIEGEL, HOST:

From NPR News, this is ALL THINGS CONSIDERED. I'm Robert Siegel.

MELISSA BLOCK, HOST:

And I'm Melissa Block.

Need a late afternoon pick-me-up? Well, Frito-Lay has a new offering on the way. In the next few weeks, it plans to introduce caffeinated coffee-flavor Cracker Jack. It's part of a growing trend of adding caffeine to snack foods and bottled water. NPR's Allison Aubrey reports on the potential downsides for tweens and teens.

ALLISON AUBREY, BYLINE: For most of us, there's nothing wrong with a little caffeine. Across the globe, it's consumed widely and usually safely. But researcher Abraham Palmer of the University of Chicago says people should realize it is a drug.

ABRAHAM PALMER: Yeah, absolutely. Caffeine is definitely a drug.

AUBREY: And it has the power to change our behavior temporarily by altering the physiology of our brains.

PALMER: And it keeps people awake. It tends to make people more talkative. And, in some people, it can cause both euphoria and also anxiety.

AUBREY: Well, one of those sound pretty good, I'll take euphoria. But anxiety, who needs it? Palmer says from person to person, there are big differences in how we respond.

PALMER: There are some of us that really enjoy caffeine, such as myself, and there are others, such as my wife, who really hate caffeine because it makes her feel jittery and anxious.

AUBREY: For lots of people, it's the amount of caffeine that's key. For those of us who've settled into a regular coffee habit, we know what we're getting. One cup may give us a boost, but more than that may leave us feeling a little jangly. So what happens when caffeine starts to turn up in foods and drinks that typically haven't contained it?

MICHAEL JACOBSON: There's a proliferation of foods from granola to maple syrup to marshmallows, all kinds of things are now being caffeinated.

AUBREY: That's Michael Jacobson of the Center for Science in the Public Interest. When I visited his office, he unpacked a whole box of caffeinated foods he's been collecting. Some are from big manufacturers like Kraft, others are niche products, for example, a caffeinated turkey jerky called Perky Jerky.

JACOBSON: It says it's a good source of protein for active lifestyles. Grab a jerk and go.

AUBREY: But I'm looking there at the nutrition facts label and nowhere do I see caffeine.

JACOBSON: Right. There's no indication as to how much caffeine is in the product.

AUBREY: It's not that manufacturers are trying to hide caffeine. In many cases, they're are promoting these foods as pick-me-ups. But Jacobson says, given that so many people are sensitive to small shifts in caffeine, the Food and Drug Administration should update its regulations. Currently, the amount of caffeine does not need to be listed on a label.

JACOBSON: I think at a minimum, the FDA should require the amount of caffeine to be disclosed on product labels.

AUBREY: Jacobson launched a high-profile complaint when Frito-Lay announced plans for their new coffee Cracker Jack snack. His view is that this is a slippery slope to escalating consumption.

JACOBSON: I think it's a real concern to add a mildly objective stimulant drug to all kinds of things and I think a special risk to kids.

AUBREY: Frito-Lay says it's not marketing the new Cracker Jacks to kids. In fact, none of the products we looked at seemed to be targeting kids. But it's clear from the flack over potential risks of energy drinks that some teens do seek out and get their hands on caffeinated products. The questions that Jacobson and others have about teens and caffeine are these: If they're introduced to caffeine, perhaps through the back door of caffeinated snacks or water, does it prime them to crave more and could that be dangerous?

Jennifer Temple of the University of Buffalo is studying how kids respond to caffeine.

JENNIFER TEMPLE: Kids are not just small adults and their brains are still developing. And so what does early caffeine would do to the developing brain?

AUBREY: In one experiment, she recruited teenagers to try a bunch of unusual flavored sodas, two kinds of them. Unbeknownst to them, one had caffeine, the other did not. They drank about four cups a day for one week. Temple wanted to know if these kids would develop stronger preferences for the secretly caffeinated drinks.

TEMPLE: It was a daily exposure to the caffeine, but it was only over the course of a week.

AUBREY: Now, at the end of the week, she brought the teens into a computer lab where they played a game to earn points to get the soda they preferred.

TEMPLE: It very quickly escalates to the point where they're working very, very hard to get the caffeinated soda.

AUBREY: The boys, in particular, worked twice as hard to get caffeine, explains Temple. But the non-caffeinated drinks, these did not motivate them at all. Now, the amount of caffeine they were getting was modest, about what you'd find in a regular cola. And at the end of the study, Temple debriefed the teens, asking them if they knew why they were motivated to work so hard for the drink.

TEMPLE: They couldn't necessarily describe why.

AUBREY: Some of the teenagers suspected that maybe caffeine was added. But what's surprising, Temple says is how quickly their preferences developed after just one week of exposure to the caffeine.

TEMPLE: If that can happen in that short a period of time, what's happening when these kids are consuming, you know, over the course of weeks and months and years?

AUBREY: Rarely do teens drink enough caffeine to do serious harm. But since consumption tends to go up once they start getting caffeine. It can, at the very least, set the stage for sweet problems or bouts of anxiety. The Food and Drug Administration is investigating the safety of energy drinks, which can contain high levels of caffeine compared to soda. But a spokesperson for the FDA says it's too soon to speculate about whether more or new regulations for caffeine are being considered.